It is known that at a construction site or along a proposed path of underground utility lines, it is necessary to lower the water table level. One method for lowering the water table is the use of horizontal well pipe. The well pipe is placed at the bottom of a trench and then back filled with the excavated earth or with substitute fill conveyed to the trench. A suction pump is attached at an above-ground end of the pipe to continuously draw up water that enters perforations in a horizontal portion of the well pipe until the water table is lowered. One such device is disclosed in U.S. Pat. No. 4,927,292 to Justice.
U.S. Pat. No. 3,753,352 to McNally discloses a perforate conduit comprising an elongated tubing with at least one series of longitudinally extending, spaced apart ridges formed in the wall of and extending outwardly from the surface of the tubing. At least one opening is provided in each of the ridges to provide a drainage opening into the tube. The ridges are formed during extrusion, and the tops are cut off to form the opening. The invention is used for land drainage, in various lengths of up to 4 feet, laid end-to-end in excavations.
U.S. Pat. No. 4,626,129 to Kothmann et al discloses a sub-soil drainage pipe segment which has connecting formations at opposite ends. A number of such segments can be interconnected end-to-end to form a sub-soil drainage line, the segment also having a plurality of circumferentially spaced, longitudinally extending slots which render the segment water pervious.
Non of the prior art devices are concerned with withdrawing sub-soil with the water as it is pumped to the surface. The sub-soil drainage pipes use gravel to block the withdrawal of sub-soil. Furthermore, the very nature of the devices, i.e., continuous flow without any consideration of withdrawal of soil would not be practical for the principle object of the invention, which is to prevent enlargement of a cable splice pit which has been dug in fluid soil.